Yes. Originally it was to be mix of GT1 and GT3 cars Ferrari and McLaren were not happy with this and would not race in championship with a mix of cars, only GT3 would do for them. And so it came about and this year the championship is only for GT3 racers. NZ driver Mike Halliday has a drive in a Porsche GT3R and won the championship race at Zolder this weekend past. Its a shame JRM arent running a pair of GTRs in it, they had a lot of technical support from NIssan/Nismo with some gun driver lineups including David Brabham who ironically is racing for JRM in the Honda LMP in WEC for them this year with Peter Dumbrek and Karun Chandok.
No idea where the GT1 GT-Rs will end up (Nissan storage, collectors, historic racing etc). Not sure who owns which cars between Nismo and JRM and if the cars were brought or leased by JRM.